As one technique for improving viewing angle dependence of γ characteristic in a liquid crystal display (difference between (i) γ characteristic in observing a liquid crystal display from the front and (ii) γ characteristic in obliquely observing the liquid crystal display), a pixel division method (so-called multi-pixel technique) for constituting each pixel by a plurality of subpixels has been suggested (refer to Patent Literature 1, for example).
FIG. 35 shows a configuration of a conventional active matrix substrate used for a pixel division method liquid crystal display. As shown in the drawing, the conventional active matrix substrate includes data signal lines 215 and scanning signal lines 216 which intersect at right angles to each other, first and second storage capacitor wirings 218a and 218b, and pixel regions 205 provided in a matrix pattern. It should be noted that a layer in which the data signal lines 215 are provided is higher than a layer in which the scanning signal lines 216 are provided. Each scanning signal line 216 extends in a row direction (horizontal direction in the drawing) so as to cross the pixel regions 205. Each data signal line 215 extends in a column direction (vertical direction in the drawing) along one side of pixel regions (edge along a direction in which the data signal line 215 intersects at right angles to the scanning signal lines 216). The first or second storage capacitor wiring 218a or 218b extends in the row direction (horizontal direction in the drawing) so as to superpose adjacent end portions of two pixel regions adjacent in the column direction.
On each pixel region 205, a switching element 212 including first and second transistors 212a and 212b, first and second pixel electrodes 217a and 217b, the first and second storage capacitor wirings 218a and 218b, first and second drain drawing wirings 227a and 227b, and first and second contact holes 211a and 211b are formed.
Here, the first and second pixel electrodes 217a and 217b are disposed on one (upper in the drawing) and the other (lower in the drawing) sides of the scanning signal line 216, respectively. The switching element 212 is provided in the vicinity of an intersection of the data signal line 215 and the scanning signal line 216. As shown in FIG. 36, each of the pixel electrodes (217a and 217b) provided in the pixel regions adjacent in the column direction is connected to the same data signal line 215 via the switching element 212.
A source electrode 209a of the first transistor is drawn in the row direction from the data signal line 215. A drain electrode 208a of the first transistor is formed so as to face the source electrode 209a and connected to the first pixel electrode 217a via the first drain drawing wiring 227a and the contact hole 211a. Furthermore, a first storage capacitor is formed on a superposition section in which the first pixel electrode 217a and the first storage capacitor wiring 218a superpose each other. Similarly, a source electrode 209b of the second transistor is drawn in the row direction from the data signal line 215. A drain electrode 208b of the second transistor is formed so as to be superposed on a second scanning electrode section 216b and face the source electrode 209b. The drain electrode 208b is connected to the second pixel electrode 217b via the second drain drawing wiring 227b and the contact hole 211b. Moreover, a second storage capacitor is formed on a superposition section in which the second pixel electrode 217b and the second storage capacitor wiring 218b superpose each other.
In a liquid crystal display including the aforementioned active matrix substrate, each pixel is formed in such a manner that (i) it is formed with the pixel region 205, and regions on a counter substrate and in a liquid crystal layer which regions correspond to the pixel region 205, (ii) a first subpixel is formed with a region on which the first pixel electrode 217a is provided, and regions on the counter substrate and in the liquid crystal layer which regions correspond to the region on which the first pixel electrode 217a is provided, and (iii) a second subpixel is formed with a region on which the second pixel electrode 217b is provided, and regions on the counter substrate and in the liquid crystal layer which regions correspond to the region on which the second pixel electrode 217b is provided.
With the aforementioned active matrix substrate, the same signal potential is supplied from the data signal line 215 to the first or second pixel electrodes 217a or 217b. However, potentials of the first and second storage capacitor wirings 218a and 218b are individually controlled so as to set the first and second pixel electrodes 217a and 217b to different potentials via the first and second storage capacitors.
Accordingly, in a liquid crystal display including the aforementioned active matrix substrate, constituting each pixel by a high-luminance subpixel (bright subpixel) and a low-luminance subpixel (dark subpixel) makes it possible to display halftone by area coverage modulation and thus viewing angle dependence of γ characteristic (e.g. excess brightness) can be improved.
As a method for driving a data signal line in a liquid crystal display, dot inversion driving (1H/1V inversion driving) is often applied. In the dot inversion driving, in the same frame, signal potentials are supplied to switching elements adjacent in the row direction so that polarities of the signal potentials are different from each other and on the other hand, signal potentials are supplied to switching elements adjacent in the column direction so that polarities of the signal potentials are different from each other. However, in the dot inversion driving, the frequency of polarity inversion on the data signal line during one frame period is high. Therefore, when this is applied particularly to a large-scale liquid crystal display, there occurs such a problem that the data signal line is insufficiently charged or power consumption is increased.
In order to solve such a problem, it is an option to apply such driving that: for the row direction, different polarities are supplied for each switching element; and for the column direction, different polarities are supplied for every two adjacent switching elements (2H/1V inversion driving, refer to Patent Literature 2, for example).